The invention relates to an actuation system for the clutch of a motor vehicle drive train having an automatic transmission and to a method for controlling an actuation system for an automatic motor vehicle clutch with an electrohydraulic actuator drive for actuating the clutch. Such an actuation system for the clutch of a motor vehicle provided with an automatic transmission has an electrically controlled actuator drive for actuating the clutch, and a position control circuit that contains a position controller determining the position of the clutch and to which a setpoint value for the position and a measurement signal, representing the position, of a sensor are fed as actual values.
In addition to the conventional motor vehicle clutches that are actuated directly by the driver, automatically actuated clutches are being increasingly used in motor vehicles (see for example German Published, Non-Prosecuted Patent Application DE 44 34 111 A1, corresponding to U.S. Pat. No. 5,993,355 to Nordgaard). In electrohydraulic clutch actuation systems, the clutch position is measured to control the position. The measured signal contains oscillations with highly variable frequencies that lie in the typical frequency range of the control and, thus, lead to undesired control movements. Such movements increase, in particular, the oil requirements of the electrohydraulic clutch actuation system. In addition, the interference signal restricts the stability range of the control circuit and reduces the system dynamics that can be achieved.
It is accordingly an object of the invention to provide an actuation system for the clutch of a motor vehicle drive train provided with an automatic transmission, and method for controlling such an actuation system that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and that provides an actuation system for an automatic motor vehicle clutch in which negative influences of interference oscillations of the clutch position signal are avoided.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a clutch actuation system for a motor vehicle having an engine connected to a drive train including a clutch, an automatic transmission, and an electrically controlled actuator drive for actuating the clutch, the actuation system including a position control circuit having a sensor sensing a position of the clutch and reproducing a position of the clutch with a position measurement signal, a controller determining the position of the clutch, the controller connected to the sensor and receiving a setpoint value for the position of the clutch and the position measurement signal as an actual position of the clutch, and a filter connected to the controller and filtering interference oscillations out of the position measurement signal, and the filter having a stop band adaptively dependent upon a rotational speed of the engine.
The advantages of the invention lie, in particular, in the fact that, with it, the energy requirements of electrically controlled clutch systems are effectively reduced, specifically both with electromechanically actuated clutches and electrohydraulically actuated clutches. In the case of the latter, in particular, the oil requirements are also reduced. The stability range of the control circuit is greater and higher system dynamics are achieved.
In accordance with another feature of the invention, the filter is a band stop filter having time-variable filter coefficients defined to present a stop frequency of the filter at the rotational speed of the engine.
In accordance with a further feature of the invention, the filter is a band stop filter having a stop band and a stop frequency corresponding to the rotational speed of the engine, and the stop band has a width less than or equal to approximately 30% of the stop frequency.
In accordance with an added feature of the invention, the filter is a Butterworth band stop filter of the second order.
In accordance with an additional feature of the invention, the filter is disposed between the controller and the actuator drive.
In accordance with yet another feature of the invention, the filter is disposed between the sensor and the controller.
In accordance with yet a further feature of the invention, the controller stores a characteristic diagram and filter coefficients are stored in the characteristic diagram as interpolation nodes for an interpolation.
With the objects of the invention in view, in a motor vehicle having an engine connected to a drive train including a clutch, an automatic transmission, and an electrically controlled actuator drive for actuating the clutch, there is also provided a clutch actuation system including a position control circuit having a sensor sensing a position of the clutch and reproducing a position of the clutch with a position measurement signal, a controller determining the position of the clutch, the controller connected to the sensor and receiving a setpoint value for the position of the clutch and the position measurement signal as an actual position of the clutch, and a filter connected to the controller and filtering interference oscillations out of the position measurement signal, and the filter having a stop band adaptively dependent upon a rotational speed of the engine.
With the objects of the invention in view, there is also provided a method for controlling an actuation system for an automatic motor vehicle clutch having an electrohydraulic actuator drive for actuating the clutch, including the steps of determining a position of the clutch with a position control circuit by feeding to the position control circuit set point values for the position of the clutch and a measured position signal of a sensor representing the position of the clutch as an actual value and filtering out interference oscillations from the position signal with a filter having a stop band dependent adaptively upon a rotational speed of a drive engine of the motor vehicle.
In accordance with yet an added mode of the invention, a band stop filter is provided as the filter and time-variable filter coefficients of the filter are defined to present a stop frequency of the filter at the rotational speed of the drive engine of the motor vehicle.
In accordance with yet an additional mode of the invention, a band stop filter is provided as the filter, filter coefficients are defined to have a stop frequency of the filter correspond to the rotational speed of the drive engine, and a width of the stop band is defined to be not more than approximately 30% of the stop frequency.
In accordance with a concomitant mode of the invention providing a band stop filter as the filter, defining filter coefficients to have a stop frequency of the filter correspond to the rotational speed of the drive engine, and defining a width of the stop band to be less than or equal to approximately 30% of the stop frequency.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an actuation system for the clutch of a motor vehicle drive train provided with an automatic transmission, and method for controlling such an actuation system, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.